Caravan DC System Reverse Charging Car

[gxl_d4d Advanced Member Find all posts View Profile Close gxl_d4d]

Hi,
I'm awaiting deliver of a new caravan. It's electrical setup is very basic, 360W solar, 30A pwm regulator and 25A (240AC to 13.6Vdc) Meanwell float charger, 2 x 100Ah batteries. My car has dual batteries under the bonnet separated by a redarc isolator (single sensing version, not dual sensing). The anderson plug on the back of my car is connected to the auxilary battery under the bonnet. The anderson plug on the caravan to the car does not have a VSR or DC DC charger. Should I expect any issues in the following scenario's:

- Driving, alternator charging all batteries in parallel and the solar regulator outputting current?
- Parked, all batteries connected in parallel due to redarc isolator still connecting the starter battery to the aux which is powering the van and the solar regulator outputting current.
- Parked, starter battery isolated due to voltage dropping sufficiently for redarc to disengage. Solar regulator outputting current. Aux battery and 2 x van batteries connected in parallel.
- Parked at a powered site, caravan AC/DC charger reverse charging car due to voltage not dropping for redarc to disengage.

The reason for the question is that I'm debating whether to bother with a DC/DC charger on the caravan to isolate my car DC system from the van when parked.

Thanks,

[sparksy Senior Member Find all posts View Profile Close sparksy]

Fit a DCDC to the van. 2 things come into account, the fridge 12v supply should really come from the starter, but Ive got mine connected to the aux, and there should be a trigger wire from car when its running in the trailer plug to switch fridge ( assuming its a 3 way AES type fridge) . If not already fitted with a dcdc then maybe the battery is charged old school from car through a diode which stops reverse current flow. A dcdc will help with charging the van battery unless you have a large cable supplying your rear anderson. I have 25mm supplying a 150A anderson.
best idea is contact the van dealer and get the list of requirements for electrical connection to your car.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

It really depends on how much power you use, if the solar meets your demand then your only relying on the DCDC to keep things charged while travelling when no sun is or has been available. Many have just relied on a straight connect for off car charging and it can work ok if you use adequate cable as per sparksy post. I originally had 25mm charging two gel cells in thye camper and it worked fine, a few years back I swapped to Lithium and found I could only get around 20A into the Lithiums so installed a DCDC charger. Recently have put 200W of solar on the roof and find I don't really need to charge off car at all, the solar keeps things going by itself but it is nice to have a fall back if the sun don't shine.

[gxl_d4d Advanced Member Find all posts View Profile Close gxl_d4d]

The largest load when parked will be the fridge, it's a compressor fridge and maybe the internal fan. At night, fridge and lights. I believe the fridge draws around 6A. I've got 6B&S twin from the engine bay to the back of the car so I don't anticipate much voltage drop in the car cabling with solar generating, the solar should hold up the volts. I think I'll run the system as delivered and see how I go. If I have issues with the caravan discharging my auxiliary car battery at night when not connected to mains, I'll look at either a VSR or DC-DC charger mounted in the caravan. I rely on the auxilary battery for a backup cranking battery so I'm keen not to have it discharge into the van. This will only be an issue when I'm connected to the car at a drive through site or roughing it.

[GeeWhizz Senior Member Find all posts View Profile Close GeeWhizz]

Get a VSR. They don't cost too much and will save your vehicle battery/s from discharging into the van's battery. If the van has working fridge/lights etc then it will draw on the vehicle's battery.

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

OR unplug car and van overnight?